PARASITIC INFECTIONS

[Audio] PARASITIC INFECTIONS So, naturalists observe, a flea hath smaller fleas that on him prey and these smaller to bite 'em; and so proceed ad infinitum..

[Audio] OBJECTIVES: AFTER STUDYING THIS CHAPTER, YOU SHOULD BE ABLE TO: Differentiate between the following: ectoparasites versus endoparasites; definitive hosts versus intermediate hosts; facultative parasites versus obligate parasites and mechanical vectors versus biological vectors. Classify a particular parasitic infection as a protozoal or helminth disease. Categorize various parasitic infections by body system. Correlate a particular parasitic infection with its major characteristics, causative agent, reservoir(s), mode(s) of transmission, and diagnostic laboratory procedures..

[Audio] INTRODUCTION PARASITOLOGY is the study of parasites; considered a branch of microbiology. However, not all organisms studied in parasitology are microbes. NATIONALLY NOTIFIABLE PARASITIC DISEASE PARASITIC DISEASE NO. OF NEW U.S. CASES REPORTED TO CDC IN 2014 CRYPTOSPORIDIOSIS 8, 682 CYCLOSPORIASIS 398 GIARDIASIS 14, 554 MALARIA 1, 653 TRICHINELLOSIS 13.

[Audio] Parasites are organisms that live on or in other living organisms, at whose expense they gain some advantage. Parasitism is a symbiotic relationship that is of benefit to one party or symbiont ( tha parasite) at the expense of the other party ( host). Ectoparasites are parasites that live outside the host's body..

[Audio] Endoparasites are parasites that live inside the host's body. Definitive host is the one that harbors the adult or sexual stage of the parasite or the sexual phase of the life cycle. Intermediate host is the one that harbors the larval or asexual stage of the parasite or the asexual phase of the life cycle..

[Audio] Accidental host is a living organism that can serve as a host in a particular parasite's life cycle, but is not a usual host in that life cycle. Dead-end hosts which the parasite cannot continue its life cycle. Facultative parasite is an organism that can be parasitic but does not have to live as a parasite..

[Audio] Obligate parasite has no choice; to survive, it must be a parasite. Parasitologist is someone who studies parasites. Medical parasitology is the study of parasites that cause human disease. Parasitology Section of the Clinical Microbiology Laboratory assist clinicians in the diagnosis of parasitic diseases..

[Audio] HOW PARASITES CAUSE DISEASE? The manner in which parasites cause damage to their host varies from one species of parasite to another, and often depends on the number of parasites that are present. Worm Burden pertains to the number of helminths present. Some parasites produce toxins; produce harmful enzyme; Invasive and migratory parasites which cause physical damage to tissue and organs; cause destruction of blood vessels and other tubular structures; interfere vital processes of host. Besides, the host immune response to the presence of parasites causes more injury than do the parasites themselves..

[Audio] PARASITIC PROTOZOA Most protozoa are unicellular, but some are multicellular (colonial). Protozoa can be classified taxonomically by their mode of locomotion. Amebas (amebae) move by means of pseudopodia; "false feet". Flagellates move by means of whiplike flagella. Ciliates move by means of hairlike cilia. Protozoa classified as Sporozoa ( sporozoans) have no pseudopodia, flagella, or cilia, and, therefore, exhibit no motility. Not all protozoa are parasitic. Pond water protozoa (e.g., Paramecium and Stentor spp.) are not parasites..

[Audio] Although most protozoal parasites of humans are obligate parasites, some are facultative parasites-- capable of a free living, nonparasitic existence, but also able to become parasites when they accidentally gain entrance to the body. Acanthamoeba spp. and Naegleria fowleri are examples of facultative parasites. These free-living amebas normally reside in soil or water, but can cause serious diseases when they gain entrance to the eyes or the nasal mucosa. From nasal mucosa, they travel via the olfactory nerve into the brain and cause diseases affecting the central nervous system ( CNS). Because protozoa are tiny, protozoal infections are most often diagnosed by microscopic examination of body fluids, tissue specimens, or feces..

[Audio] Peripheral blood smears are usually stained with Giemsa stain, whereas fecal specimens are stained with trichrome, iron hematoxylin, or acid-fast stains. Most parasitic protozoal infections are diagnosed by observing trophozoites, cysts, oocysts, or spores in the specimen. The trophozoites is the motile, feeding, dividing stage in a protozoan's life cycle. Cysts, oocysts, and spores are dormant stages (much like bacterial spores). Protozoal infections are primarily acquired by ingestion or inhalation of cysts, oocysts, or spores, or injection via the bite of an infected arthropod. Because of their fragile nature, only rarely do trophozoites serve as the infective stages..

[Audio] PROTOZOAL INFECTIONS OF HUMANS. abstract.

[Audio] PROTOZOAL INFECTIONS OF THE SKIN LEISHMANIASIS Disease. Leishmaniasis is caused by various species of flagellated protozoa and is usually transmitted via the bite of an infected sand fly. Three forms of leishmaniasis: cutaneous, mucocutaneous (or mucosal), and visceral. The cutaneous form starts with a papule that enlarges into a craterlike ulcer. Individual ulcers may coalesce, causing severe tissue destruction and disfigurement. Visceral leishmaniasis, also known as kala-azar, is characterized by fever, enlarged liver and spleen, lymphadenopathy, anemia, leukopenia, and progressive emaciation and weakness. Death may result in untreated cases. Patient care. Use Standard Precautions for hospitalized patients..

[Audio] Geographic Occurrence. Leishmaniasis occurs in many regions of the world, including Pakistan, India, China, the Middle East, Africa, South and Central America, and Mexico. Cases have also occurred in South Central Texas. It is estimated that between 1.5 and 2 million people have leishmaniasis and that about 57,000 people die each each year of the disease. Parasites. Leishmaniasis is a caused by various species of flagellated protozoa in the genus Leishmania, and is usually transmitted via the bite of an infected sand fly. Amastigote is the non-motile, intracellular form of the parasite. Promastigote is the motile, extracellular form of the parasite..

[Audio] Reservoirs and Mode of Transmission. Reservoirs include infected humans, domestic dogs, and various wild animals. Leishmaniasis is principally a zoonosis and is usually transmitted via the bite of an infected sand fly. Transmission by blood transfusion and person-to-person contact have been reported..

[Audio] Laboratory Diagnosis. Diagnosis of cutaneous and mucocutaneous leishmaniasis is made by microscopic identification of the amastigote form in stained preparations from lesions or by culture of the extracellular promastigote form on suitable media. An intradermal test, called the Montenegro test, and immunodiagnostic and molecular diagnostic procedures are also available. In the Montenegro test, an antigen derived from promastigotes is injected into the skin..

[Audio] PROTOZOAL INFECTIONS OF THE EYES Protozoal infections of the eyes include conjunctivitis and keratoconjunctivitis ( inflammation of the cornea and conjunctiva), caused by amebas in the genus Acanthamoeba, and toxoplasmosis, caused by the sporozoan, Toxoplasma gondii. Ocular manifestations of toxoplasmosis occur primarily in immunosuppressed patients, in whom the infection can lead to removal of the infected eyeball ( enucleation)..

[Audio] AMEBIC EYE INFECTIONS Disease. Amebic Conjunctivitis and Keratoconjunctivitis; causes inflammation of the conjunctiva, corneal ulcers, pus formation, and severe pain. It can lead to loss of vision. The disease process is more rapid if corneal abrasions are present. Parasites. Amebic eye infections are caused by several species of amebas in the genus Acanthamoeba..

[Audio] Reservoirs and Mode of Transmission. The amebas enter the eye from ameba-contaminated waters. Laboratory Diagnosis. Amebic eye infections are diagnosed by microscopic examination of scrapings, swabs, or aspirates of the eye, or by culture on media seeded with Escherichia coli or another member of the family Enterobacteriaceae. The bacteria on the media serve as food for the amebas..

[Audio] TOXOPLASMOSIS Disease. Toxoplasmosis is a systemic sporozoan infection that, in immunocompetent persons, may be asymptomatic or resemble infectious mononucleosis. Cerebral toxoplasmosis is common in AIDS patients. Infection during early pregnancy may lead to fetal infection, causing death of the fetus or serious birth defects (e.g., brain damage). Ocular manifestations of toxoplasmosis occur primarily in immunosuppressed patients, in whom the infection can lead to removal of the infected eyeball ( enucleation)..

[Audio] Parasite. Toxoplasmosis is caused by Toxoplasma gondii, an intracellular sporozoan. Reservoirs and Mode of Transmission. Definitive hosts include cats and other felines that usually acquire infection by eating infected rodents or birds. Intermediate hosts include rodents, birds, sheep, goats, swine, and cattle. Humans usually become infected by eating infected raw or undercooked meat (usually pork or mutton) containing the cyst form of the parasite or by ingesting oocysts that have been shed in the feces of infected cats. Oocysts may be present in food or water contaminated by feline feces. Children may ingest oocysts from sand boxes containing cat feces. Infection can also be acquired transplacentally, by blood transfusion, or by organ transplantation..

[Audio] PROTOZOAL INFECTIONS OF THE GASTROINTESTINAL TRACT Of the many protozoal infections of the gastrointestinal tract, only amebiasis, balantidiasis, cryptosporidiosis, cyclosporiasis, and giardiasis are mentioned in this chapter. Cryptosporidium parvum, a protozoan parasite. The parasite that caused the largest waterborne outbreak ever to occur in the United States..

[Audio] PROTOZOAL INFECTIONS OF THE GENITOURINARY TRACT TRICHOMONIASIS Disease. Trichomoniasis is a sexually transmitted protozoal disease affecting both men and women. Trichomoniasis is caused by a flagellated protozoan named vaginalis and is transmitted by direct contact with vaginal and urethral discharges of infected people. Symptomatic in females. Asymptomatic in males. The disease is usually symptomatic in women, causing vaginitis with a profuse, thin, foamy, malodorous, greenish-yellowish discharge. In women, trichomoniasis may also present as urethritis or cystitis..

[Audio] Because this organism exists only in the fragile trophozoite stage (there is no cyst stage), it cannot survive very long outside the human body. Laboratory Diagnosis. Vaginitis caused by T. vaginalis can be diagnosed by performing a saline wet mount examination of freshly collected vaginal discharge material and observing the motile trophozoites..

[Audio] Patient Care. Use Standard Precautions for hospitalized patients Geographic Occurrence. Trichomoniasis occurs worldwide. Parasite. T. vaginalis, a flagellate. Reservoirs and Mode of Transmission. Infected humans serve as reservoirs. Transmission occurs by direct contact with vaginal and urethral discharges of infected secretions..

[Audio] PROTOZOAL INFECTIONS OF THE CIRCULATORY SYSTEM AFRICAN TRYPANOSOMIASIS ( AFRICAN SLEEPING SICKNESS) Disease. African trypanosomiasis is a systemic disease caused by flagellated protozoa in the bloodstream, known as hemoflagellates. Early stages of the disease include a painful chancre at the site of a tsetse fly bite, fever, intense headache, insomnia, lymphadenitis, anemia, local edema, and rash. Later stages of the disease include body wasting, falling asleep, coma, and death in untreated. Patient Care. Use Standard Precautions for hospitalized patients..

[Audio] Geographic Occurrence. African trypanosomiasis is transmitted by the tsetse fly ( genus Glossina), so the disease occurs only in tropical Africa, where tsetse flies are found. Pathogens. Two subspecies of Trypanosoma brucei cause African trypanosomiasis. Trypanosoma brucei ssp. gambiense in Western and Central Africa. Trypanosoma brucei ssp. rhodesiense in Eastern Africa..

[Audio] Reservoirs and Mode of Transmission. Infected humans serve as reservoirs of T. brucei ssp. gambiense. Wild animals and domestic cattle are the primary reservoirs of T. brucei ssp. rhodesiense. Humans become infected when mature trypanosomes ( trypomastigotes) are injected into the bloodstream because the infected tsetse flies take blood meals. Laboratory Diagnosis. African trypanosomiasis is diagnosed by observing and identifying trypomastigotes in blood, lymph node aspirates, or CSF..

[Audio] AMERICAN TRYPANOSOMIASIS ( CHAGAS DISEASE) Disease. American trypanosomiasis is also known as Chagas disease. Carlos Chagas described the entire life cycle of Trypanosoma cruzi in 1909. In the acute stage of the disease, patients may present with an inflammatory response at the site of the reduviid bug bite, fever, malaise, lymphadenopathy, hepatomegaly (enlarged liver), and splenomegaly (enlarged spleen), although it may be asymptomatic. Chronic irreversible complications include heart damage, arrhythmias, enlarged esophagus, and enlarged colon. Life-threatening may occur..

[Audio] Patient Care. Use Standard Precautions for hospitalized patients. Geographical Occurrence. Chagas disease occurs primarily in South America, Central America, and Mexico. Parasite. The etiologic agent of American trypanosomiasis is T. cruzi, which occurs in two stages: A hemoflagellate (the trypomastigote form). A nonmotile, intracellular parasite (the amastigote form)..

[Audio] Reservoirs and Mode of Transmission. Reservoirs include infected humans and more than 150 species of domestic and wild animals; dogs, cats, rodents, carnivores, and primates. The vectors of American trypanosomiasis are rather rather large bugs. A bug becomes infected when it takes a blood meal from an infected animal. Later, when the bug takes a blood meal or feeds at the corner of a sleeping person's eyes, the bug defecates. Romaña sign is the characteristic unilateral swelling of the eyelid that occurs after T. cruzi is rubbed into the eye..

[Audio] Laboratory Diagnosis. American trypanosomiasis is diagnosed by observation of trypomastigotes in blood or amastigotes in tissue (especially cardiac tissue) or lymph node biopsies. Immunodiagnostic and molecular diagnostic procedures. Xenodiagnosis s performed in endemic countries. The bugs are then taken to a laboratory, where their feces are periodically checked microscopically for the presence of the parasite..

[Audio] BABESIOSIS Disease. Babesiosis is a sporozoan disease that may include fever, chills, myalgia, fatigue, jaundice, and anemia. It is potentially severe and sometimes fatal, especially in splenectomized and elederly people. Parasites. Babesiosis is caused by Babesia microti and other Babesia spp., including Babesia divergens in Europe..

[Audio] Geographic Occurrence. Babesiosis is an endemic disease in many parts of the world, including Europe, Mexico, and the United States. Reservoirs and Mode of Transmission. Reservoir include rodents for B. microti and cattle for B. divergens. Transmission occurs by tick bite and, rarely, by blood transfusion. Laboratory Diagnosis. Babesiosis is diagnosed by observation and identification of intraerythrocytic Babesia parasites in Giemsa-stained blood smears..

[Audio] MALARIA Disease. Malaria is a systemic sporozoan infection with malaise, fever, chills, sweating, headache, and nausea. The frequency with which the cycle of chills, fever, and sweating is repeated is referred to as periodicity. The intermittent bouts of chills and fever are sometimes referred to as paroxysms. Patient Care. Use Standard Precautions for hospitalized patients..

[Audio] Geographic Occurrence. Malaria is one of the most important infectious diseases in the world. It is a major health problem in many tropical and subtropical countries, with an estimated 300- 500 million cases and 1.5- 2.7 millions deaths annually. Parasites. Human malaria is caused by four species in the genus Plasmodium: Plasmodium vivax the most common. P. falciparum the most deadly Plasmodium malariae Plasmodium ovale.

[Audio] Reservoirs and Mode of Transmission. Infected humans and infected mosquitoes serve as reservoirs. Most human infections occur as a result of injection of sporozoites into the bloodstream by an infected female Anopheles mosquito. Infection may also occur as a result of blood transfusion or the use of blood- contaminated needles and syringes. Laboratory Diagnosis. Malaria is diagnosed by observation and identification of intraerythrocytic plasmodium parasites in Giemsa-stained blood smears. Immunodiagnostic and molecular diagnostic procedures are also available for diagnosis..

[Audio] PROTOZOAL INFECTIONS OF THE NERVOUS SYSTEM PRIMARY AMEBIC MENINGOENCEPHALITIS (PAM) Disease. PAM is an amebic disease causing inflammation of the brain and meninges, sore throat, severe frontal headache, hallucinations, nausea, vomiting, high fever, and stiff neck. If not diagnosed and treated promptly, death occurs within 10 days, usually on the fifth or sixth day. Patient Care. Use Standard Precautions for hospitalized patients..

[Audio] Geographic Occurrence. PAM has been reported worldwide. Parasites. PAM is caused by N. fowleri, an amoeboflagellate. Amebas in the genera Acanthamoeba and Balamuthia can cause similar conditions..

[Audio] Reservoirs and Mode of Transmission. Water and soil serve as reservoirs. The amebas usually enter the nasal passages of a person diving and/or swimming in ameba-contaminated water, such as ponds, and lakes. N. Fowleri is classified as an amoebaflagellate because its life cycle consists of 3 stages: trophozoite, a temporary flagellar stage known as amoeboflagellate, and cyst. Laboratory Diagnosis. Diagnosis of PAM can sometimes be made by microscopic examination of wet mount preparations of fresh cerebrospinal fluid..

[Audio] HELMINTHS The word helminth means parasitic worm. Although helminths are not microorganisms, the various procedures used to diagnose helminth infections are performed in the Parasitology Section of the Clinical Microbiology Laboratory. Helminths infect humans, other animals, and plants. The helminths that infect humans are always endoparasites..

[Audio] Helminths are multicellular, eukaryotic organisms in the Kingdom Animalia. The two major divisions of Helminths are roundworms ( nematodes) and flatworms. The flatworms are further divided into tapeworms ( cestodes) and flukes ( trematodes). The typical helminth life cycle includes three stages: The egg The larvae The adult worm.

[Audio] Adults produce eggs, from which larvae emerge, and the larvae mature into adult worms. Adult nematodes are either male or female. Cestodes and many trematodes are hermaphroditic; adult worms contain both male and female reproductive organs. Intermediate host is the host that harbors the larval stage. Definitive host is the host that harbors the adult worm. Sometimes helminths have more than one intermediate host and more than one definitive host..

[Audio] Helminth infections are primarily acquired by ingesting the larval stage, although some larvae are injected into the body via the bite of infected insects, and others enter the body by penetrating skin. Helminth infections are usually diagnosed by observing whole worms or segments of worms in clinical specimens (usually, fecal specimens), or larvae or eggs in the stained or unstained clinical specimens..

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[Audio] Kindly pause and read.. Circulatory System Central Nervous System Filariasis Schistosomiasis (also known as bilharzia) Cysticercosis Hydatid cyst disease Wuchereria bancrofti (N) and Brugia malayi (N); microfilariae of these helminths are found in the bloodstream Trematodes in the genus Schistosoma Cysts (the larval stage) of the pork tapeworm (Taenia solium) are found in the brain Echinococcus granulosis (C) or Echinococcus multilocularis (C); in addition to the brain, hydatid cysts (the larval form of these helminths) can form in many other locations in the body N, nematode; C, cestode; T, trematode..

[Audio] APPROPRIATE THERAPY FOR PARASITIC INFECTIONS Recommendations for the treatment of infectious diseases change frequently. The parasitic infections described must be treated using appropriate antiprotozoal or antihelminth drugs. Drugs used to treat helminth infections are also known as: Anthelmintics Anthelminthics Antihelmintics Antihelminthics.

[Audio] MEDICALLY IMPORTANT ARTHROPODS There are many classes of arthropods, but only three are studied in a parasitology course: insects (class Insecta), arachnids ( class Arachnida), and certain crustaceans (class Crustacea). The insects studied include lice, fleas, flies, mosquitoes, and reduviid bugs. Arachnids include mites and ticks. Crustaceans include crabs, crayfish, and certain Cyclops species..

[Audio] Arthropod ectoparasites and vectors of human infectious diseases. (A) Dermacentor andersoni, the wood tick; one of the tick vectors of Rocky Mountain spotted fever. ( B) Xenopsylla cheopis, the oriental rat flea; the vector of plague and endemic typhus. (C) Pediculus humanus, the human body louse; a vector of epidemic typhus. ( D) Phthirus pubis, the pubic louse; because of its appearance, it is also known as the crab louse..

[Audio] Thank you, hoped you learn something new! Reported by Group D: Almagro, Cedro, Majan, Ordonez, Osorio, and Rasalan.